Detecting small magnetic fields by means of large magnetoresistance changes while using up as little chip surface area as possible and with a low level of manufacturing-process complexity is becoming increasingly important for applications in automotive and industrial electronics. In this context, it is particularly important to achieve compatibility and optimization of parameter swing, or signal swing (change in the magnetoresistance as a function of a change in the magnetic field), chip surface area, manufacturing-process complexity, current consumption, etc.
In sensor technology, currently GMR structures (GMR=giant magnetoresistance) or TMR structures (TMR=tunneling magnetoresistance) are frequently used. GMR and TMR structures will be summarized below using the term xMR structures. In electric contacting of such xMR structures or xMR layer systems, one differentiates between a CIP configuration (CIP=current in plane) and a CPP configuration (CPP=current perpendicular to plane). In the CIP configuration, an xMR layer system is contacted from one side, and a current flow follows such that it is essentially parallel or lateral to the layer system, whereas in the CPP configuration, an xMR layer system is contacted from two sides, so that a current flow may occur such that is essentially perpendicular to the xMR layer system. GMR layer systems are commonly operated in the CIP configuration, which is associated with a relatively small amount of effort in terms of process engineering on account of contacting from one side at a layer package or at a layer structure. On the other hand, TMR layer systems are often operated in the CPP configuration, which may use contacting the layer package or layer system from two sides. However, there are also TMR layer systems which may be operated in a CIP configuration, which shall be referred to as a CIPT configuration (i.e., a CIP configuration with a TMR layer system). Contacting the layer system from one side only (above or below) allows a simpler manufacturing process as compared to contacting from both sides, as is the case in the CPP configuration.
Spin-valve magnetic sensors based on GMR or TMR technology have advantages over Hall and AMR technologies (AMR=anisotropic magnetoresistance), as are established today, in particular with respect to their measuring sensitivities. On account of their reference magnetization, useful for operation, GMR and/or TMR elements (xMR elements) are suited to sense both magnetic field directions and field strengths. In an implementation as a linear field sensor, xMR elements may be employed, for example, for detecting rotational speeds of pole wheels and/or of toothed wheels influencing a magnetic field (bias magnetic field) (so-called speed sensors). To this end, xMR spin-valve sensors may be spaced apart at a distance of about half a pole distance or tooth distance of a transmitter wheel and may be connected to form a Wheatstone bridge or half-bridge. Thus, a differential output signal may be obtained by means of a differential magnetic field by spatially separating Wheatstone bridges.